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04/24/10
SC

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Big Idea Negative numbers help us to model real world situations.
Investigation 3: Subtracting integersEssential question #3: How do I find the difference between integers?

A.

1. Complete the addition sentence -17+13=?
-17+13=4
2. Write a subtraction sentence that "undoes" the addition sentence you found in part 1.
4-(-13)=17

B.
1.Complete the addition sentence -4+-18=?
-4+(-18)=-22
2. Write a subtraction sentence that "undoes" the addition sentence you found in part 1.
22-4=18


C. Write a subtraction sentence that solves each problem.
1. ?+-18=6(?=24)
24-6=18
2. ?+-13=-41 (?=-28)
-28-(-41)=13
3. ?+6.1=-3.2 (?=-9.3)
3.2-9.3=-6.1
4. ?+(-1/3)=1/3 (?=2/3)
1/3-(-1/3)=2/3

D. Write an addition sentence that solves each problem.
1. ?-(-6)=-6 (?=0)
0+(-6)=-6
2. ?-(-2)=3 (?=1)
-1+3=2
3. ?-5.3=-7.1 (?=1.8)
7.1+(-5.3)=1.8
4. ?-(-1/4)=-3/4(?=-1)Write a subtraction sentence that is related to the addition sentence you found in part a.
-2.6-3.8=

-3/4+(-1/4)=-1


Follow up
1. Can you write a different subtraction sentence to go with 3+11=14?
14-11=3

2. a. Complete the addition sentence 3.8+(-2.6)=?
3.8+(-2.6)=1.2

b. Write a subtraction sentence that is related to the addition sentence you found in part a.
3.8-​1.2=2.6

3. a. Complete the subtraction sentence -11-6=?
-11-6=-17
b. Write a addition sentence that is related to the subtraction sentence you found in part a.
-17+6=-11

4. When you add positive and negative integers, sometimes you get a positive sum and sometimes you get a negative sum. Is the same true when you subtract positive and negative integers? Explain.
Yes, because it depends wich integer has more of a larger absolute value and if it is a positive and negative integer.